POS1456 DIAGNOSTIC ACCURACY OF THE LABIAL SALIVARY GLAND BIOPSY INCREASES WHEN OTHER HISTOPATHOLOGICAL PARAMETERS BESIDES FOCUS SCORE ARE TAKEN INTO ACCOUNT IN PRIMARY SJÖGREN’S SYNDROME
Authors: M. S. Van Ginkel, U. Nakshbandi, S. Arends, E. A. Haacke, S. C. Liefers, G. M. Verstappen, J. F. Van Nimwegen, E. Brouwer, A. J. Stel, F. K. L. Spijkervet, A. Vissink, H. Bootsma, B. Van der Vegt, F. G. M. Kroese
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Salivary gland biopsies play an important role in the classification and diagnosis of primary Sjögren's syndrome (pSS). Currently, salivary gland biopsies are considered positive for pSS if the focus score (FS), calculated by the number of characteristic lymphocytic periductal infiltrates per 4 mm2, is ≥1. However, the FS has several limitations, and other histopathological parameters, such as (pre-)lymphoepithelial lesions, IgA/IgG plasma cell shift and germinal centers can also be present in salivary glands of pSS patients. Although the diagnostic value of these histopathological features in pSS was already shown separately, no study explored the added diagnostic value of these histopathological parameters together. <h3>Objectives</h3> To evaluate the diagnostic accuracy of the labial salivary gland biopsy based on multiple histopathological parameters (FS, (pre-)lymphoepithelial lesions, IgA/IgG plasma cell shift and germinal centers) in patients suspected for pSS. <h3>Methods</h3> Consecutive sicca patients who were clinically suspected for pSS and underwent a labial gland biopsy were included. Classification of patients as pSS or non-SS was based on clinical vignettes scored by an expert panel of three experienced rheumatologists. Labial gland biopsies were analyzed for the four histopathological parameters: focus score (FS) and presence of (pre-)lymphoepithelial lesions, IgA/IgG plasma cell shift and germinal centers. Sensitivity and specificity of these histological parameters were calculated, and ROC analysis was used to determine the optimal cut-off value for the number of histopathological parameters needed to diagnose pSS. <h3>Results</h3> Of the 103 included patients, 38 patients were classified as pSS and 65 as non-SS sicca by the expert panel. In pSS patients, the prevalence of FS≥1 was 82%, followed by 68% for presence of (pre-)lymphoepithelial lesions, 63% for plasma cell shift and 24% for germinal centers. FS≥1 showed the highest sensitivity for pSS (82%), but specificity was higher for the other three parameters (98-100%, Table 1). Although the sensitivity of presence of ≥2 (out of 4) histopathological parameters was comparable to the sensitivity to FS alone, the specificity of presence of ≥2 (out of 4) histopathological parameters increased with 12% to 100%. Regarding the biopsy item in the ACR-EULAR criteria, specificity increased from 84% to 95% when FS≥1 was replaced by the presence of ≥2 histopathological parameters. <h3>Conclusion</h3> The diagnostic accuracy of the labial gland biopsy increases when other histopathological parameters besides FS are taken into account. Also, the performance of the ACR-EULAR criteria increases when the biopsy item is replaced by the presence of ≥2 histopathological parameters. This will lead to a lower number of false positive biopsies and a lower number of patients misclassified as pSS. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.